No one quite understands the neuronal changes that govern reward-directed learning. A paper in this week’s Nature helps to clarify the synaptic mechanisms involved.

Patricia Janak and colleagues trained rats to self-administer a sugar reward. They showed that reward learning depends on increased activity and synaptic strength in the amygdala, a brain region important for emotional-based learning.

The level of learning attained by individual animals correlated well with the degree of synaptic strength enhancement ? enabling the team to identify a key mechanism that could underlie goal-directed behaviour.